The immune system is the most important defense system for body to eliminate the invasion of pathogenic microorganisms, and eliminate senescent, injured and diseased cells, thereby, can maintain its own stability. Immune enhancement drugs can improve the biological activity of the histocyte of immune system, increase the growth of immune cells and the synthesis of antibodies in body, regulate the body's immune function, and maintain the body's environment balance, so as to improve the disease resistance of the body. At present, immune enhancement drugs has been widely used in anti-tumor, all kinds of infectious diseases and secondary immunodeficiency diseases adjuvant treatment [Hadden, J. W. Immunostimulants. Trends in Pharmacological Sciences, 1993, 14: 169-174]. Fungi form an important natural active compound repository, and a lot of fungi extracts and polysaccharides thereof have immune enhancement effect. Such as lentinan proves to be a kind of immunity activator, which can activate macrophages and lymphocytes. Schizophyllan has a significant cellular immune enhancement effect, and has effects on nonspecific immune system, so then can strengthen the body immunity. The schizophyllan is non-toxic, so is used for treatment of leukemia and chronic hepatitis. Therefore, the development of fungi polysaccharides for disease prevention and treatment has an important use value.
Fusarium oxysporum is a representative rhizosphere fungus, and is also a widespread plant endophytic fungus. Currently, the studies on the Fusarium oxysporum mainly concentrate in plant pathogenic mechanism, molecular biology and biological control, the latest study indicates that polysaccharides from the Fusarium oxysporum have in vitro antioxidant activity [Li, P., Luo, C., Sun, W., et al. In vitro antioxidant activities of polysaccharides from endophytic fungus Fusarium oxysporum Dzf17. African Journal of Microbiology Research, 2011, 5: 5990-5993], but the immune enhancement effect of the water extracts and polysaccharides from the Fusarium oxysporum has not been reported at home and abroad.
Macrophages are the first defense line for host to resist microbial pathogens, which are both main antigen-presenting cells and immune effector cells, can kill pathogenic microorganisms and tumor cells directly, and act an important role in the nonspecific immunity. Activated macrophages secrete nearly a hundred kinds of bioactive substances, such as NO, IL-1, TNF-α etc, these immunological active factors that act as the endogenous signals of interaction between cells play an important role in regulating the body's immune response [Adams, D. O. and Hamilton, T. A. The cell biology of macrophage activation. Annual Review of Immunology, 1984, 2: 283-318; Aderem, A. and Underhill, D. M. Mechanisms of phagocytosis in macrophages. Annual Review of Immunology, 1999, 17: 593-623]. For example, IL-1, IL-2 can promote the proliferation of T cells, promote B cells to produce antibodies, and enhance the kill ability of tumor-specific killer cells and natural killer cells. TNF-α has a direct cytotoxic effect and a growth inhibition effect to tumor cells. NO has perfectly capable of killing tumor cells and microbial pathogens. Therefore, fungi extracts or compounds that strengthen the ability of macrophages can be used in lower immune function diseases or tumor adjuvant treatment.